TABLE 1-1 Risk factors for lung-cancer

• Active cigarette-smoking

• Passive cigarette-smoking

• Radon

• Occupational carcinogens:

Arsenic

Asbestos

Chromates

Chloromethyl ethers

Nickel

• Polycyclic aromatic hydrocarbons

• Family history

• Fibrotic lung disorders

• Ambient air pollution

committees and others by committees of the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiological Protection (ICRP). The BEIR IV report (NRC 1988) reviewed the principal risk models published through the 1980s. Those models were based on either the dosimetric or the epidemiologic approach. In the dosimetric approach, a model is used to estimate the dose from alpha-particles delivered to the lung; the lung-cancer risk is then estimated with a risk coefficient based on risks in populations exposed to low linear-energy-transfer (low-LET) radiation, such as the Japanese atomic-bomb survivors, and adjusted for the greater potency of alpha radiation by using a quality factor for the relative biologic effectiveness (RBE) of alpha radiation in causing cancer, historically assumed to be the same as the ICRP quality factor of 20. The epidemiologic approach employs a risk model based on the studies of underground miners. The BEIR IV committee analyzed data from 4 cohorts of underground miners, using regression methods to develop a model that described the relationship between excess relative risk and exposure to radon progeny during 3 temporal periods of time since exposure. The model also incorporated an age dependence of the effect of radon on lung-cancer risk.

After the BEIR IV (NRC 1988) report, 2 new risk models were reported, both based on the epidemiologic approach. ICRP addressed exposures at home and at work in its Publication 65: Protection Against Radon-222 at Home and at Work (ICRP 1994a). That report used a model for excess relative risk that incorporated time dependence of the effect of radon; the risk coefficient was that reported by the BEIR IV committee. The 2nd model was based on an extensive pooled analysis of data on 11 cohorts of underground miners (Lubin and others 1995). The general analytic approach followed that of the BEIR IV committee. The models for excess relative risk incorporated exposure during windows defined by time since exposure and included age-dependence of the effect of radon. The rate at which exposure was received also had an important effect on lung-



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